Nearly 20% of species residing in UNESCO’s world heritage marine sites live in unsuitably warm waters

Sub: Sci

Sec: Biodiversity

Context:

Nearly 20% of species in 21 UNESCO World Heritage marine sites are living at or beyond their thermal limits, making them vulnerable to temperature changes.
The report, Engaging Communities to Safeguard Ocean Life, highlights the effects of ocean warming on marine species and ecosystems.

Key Findings:

Species Affected: 881 species out of 4,406 mapped are at risk, including: 342 fish species, 135 algae species, 76 mollusc species.
- 5 mammal species: Atlantic bottlenose dolphin, West Indian manatee, southern elephant seal, True’s beaked whale, Crabeater seal
- 7 shark species: Lesser sandshark, Whitespotted eagle ray, Caribbean reef shark, Southern stingray, Krefft’s ray, Lemon shark, Yellow stingray
Thermal Limit Hotspots:
- Belize Barrier Reef: 53% of species living near their thermal limits.
- Coiba National Park (Panama): 26.6% of species at risk.
- Everglades National Park (USA): 24.4% of species at risk.
- Banc d’Arguin National Park (Mauritania): 23.9% of species at risk.
- Sundarbans (Bay of Bengal): 19.8% of species living beyond thermal limits.
Ocean Heat Trends:
- Global sea surface temperature (SST) is 1°C higher than 140 years ago.
- Ocean heat content has impacted all the six major oceans since 1998. The Southern Ocean has seen the most significant warming since 1998.

Implications of Ocean Warming:

Adaptation or Migration:
- Species may migrate to cooler waters, but some may not adapt effectively.
- Tropical species are particularly vulnerable due to limited recent exposure to high temperatures.
Reproductive Stress:
- Warm waters impair reproductive rates (e.g., female sperm whales struggle to conceive).
- Stress levels in marine mammals rise, reducing survival rates.
Food Chain Disruption:
- Species like North Atlantic right whales face food shortages due to prey migration.
- Key habitats for fish, lobsters, oysters, and crabs are shifting.
Oxygen and Nutrient Cycles:
- Changes in water movement reduce oxygen levels and nutrient circulation.
- Altered bacterial behavior impacts water and atmospheric characteristics.
Pathogen Vulnerability:
- Migrating species are exposed to new pathogens, increasing disease risks.